one of four runways at sfo. most of the time it's one of the two runways used for arrivals and departure of the larger planes like the boeing 777 and others used for international flights. >> investigators will less tone the conversations made from the air traffic control towers as they try to piece together what happened. here's a sample of what they will listen to. >> asiana 214, emergency vehicles are responding. they are en on their way. >> some of the audio is difficult to make out. but you can hear the tower telling the pilot who radioed in that emergency vehicles were on their way. this conversation happened in moment right after the crash. >> we talked to abc7 news aviation consultant john nance what he believes likely went wrong. >> we know it was too low obviously, we know it was too slow, and the combination of that with the nose up angle, of course, which is what we were told at first, that there was a major problem in trying to make the runway. and the missing element here is power. now did they pus